Isesaki climate

Name: Isesaki
Address: JP

Isesaki is warmest in August, with average highs of 29 °C, and coldest in January, when nights average -1.9 °C. September is the wettest month (205 mm) and December the driest (46 mm). Figures are 1991–2020 climate normals.

Across a full year Isesaki averages 1,476 mm of rain, 83 days above 25 °C and 70 days below freezing.

Japan · population 211,850 · 1991–2020 normals

Temperature below 0 °C to above 30 °C Rain band height is that month’s share of the wettest month

Warmest month August 29 °C
Coldest month January -1.9 °C
Driest month December 46 mm
Wettest month September 205 mm
Least cloud December 39 % cloud
Hottest on record July 40 °C
Coldest on record January -14 °C

What to expectIsesaki through the year

Isesaki has a clear annual cycle: average daily highs run from 6.6 °C in January to 29 °C in August, a swing of 23 °C in mean temperature across the year.

Counted across a normal year, 83 days a year reach 25 °C, 22 of them reach 30 °C, 70 nights drop below freezing. The warmest reading in the 1991–2020 record is 40 °C, in July.

Rain is strongly seasonal. September averages 205 mm against 46 mm in December — 4.4 times as much. Planning around the dry months matters more here than planning around temperature.

Month by month

Month	Avg high	Rainfall	Cloud
January	6.6 °C	54 mm	40 %
February	7.6 °C	54 mm	46 %
March	11.4 °C	96 mm	54 %
April	16.9 °C	108 mm	58 %
May	21.6 °C	133 mm	66 %
June	24.1 °C	178 mm	79 %
July	27.5 °C	194 mm	77 %
August	28.6 °C	155 mm	69 %
September	24.7 °C	205 mm	69 %
October	19.3 °C	186 mm	60 %
November	14.2 °C	66 mm	47 %
December	9.3 °C	46 mm	39 %

Temperature month by month

Month	Avg high	Avg low	Mean	Record high	Record low	Days above 25 °C	Days above 30 °C	Days below 0 °C
January	6.6 °C	-1.9 °C	1.8 °C	16.7 °C	-13.6 °C	0	0	24
February	7.6 °C	-1.4 °C	2.6 °C	20.2 °C	-12.2 °C	0	0	20
March	11.4 °C	1.7 °C	6.2 °C	23.2 °C	-7.6 °C	0	0	11
April	16.9 °C	6.9 °C	11.7 °C	28.9 °C	-4.0 °C	1	0	1
May	21.6 °C	12.2 °C	16.7 °C	34.7 °C	2.4 °C	5	0	0
June	24.1 °C	16.8 °C	20.3 °C	34.6 °C	8.6 °C	11	2	0
July	27.5 °C	20.6 °C	23.9 °C	39.6 °C	13.9 °C	23	8	0
August	28.6 °C	21.7 °C	24.9 °C	38.3 °C	14.6 °C	27	11	0
September	24.7 °C	18.2 °C	21.2 °C	34.1 °C	8.0 °C	14	1	0
October	19.3 °C	12.1 °C	15.5 °C	30.1 °C	1.9 °C	1	0	0
November	14.2 °C	5.7 °C	9.6 °C	24.1 °C	-1.3 °C	0	0	1
December	9.3 °C	0.7 °C	4.5 °C	21.0 °C	-7.8 °C	0	0	14

Rain, sun and wind month by month

Month	Rainfall	Wet days	Daylight	Cloud cover	Humidity	Wind
January	54 mm	6	10.0 h/day	40 %	65 %	16 km/h
February	54 mm	7	11 h/day	46 %	64 %	17 km/h
March	96 mm	11	12 h/day	54 %	67 %	17 km/h
April	108 mm	11	13 h/day	58 %	69 %	16 km/h
May	133 mm	12	14 h/day	66 %	73 %	14 km/h
June	178 mm	17	15 h/day	79 %	80 %	12 km/h
July	194 mm	17	14 h/day	77 %	83 %	10 km/h
August	155 mm	16	14 h/day	69 %	81 %	10 km/h
September	205 mm	16	12 h/day	69 %	81 %	11 km/h
October	186 mm	12	11 h/day	60 %	78 %	11 km/h
November	66 mm	7	10 h/day	47 %	74 %	13 km/h
December	46 mm	6	9.7 h/day	39 %	68 %	15 km/h

How Isesaki compares

The same four figures for nearby destinations, so the numbers above have something to be read against. Summer high is the warmest month's average high; winter low is the coldest month's average low.

Destination	Summer high	Winter low	Rain per year	Days above 25 °C
Isesaki	29 °C	-1.9 °C	1,476 mm	83
Maebashi · Japan	29 °C	-2.0 °C	1,577 mm	83
Ōta · Japan	30 °C	-1.6 °C	1,478 mm	93
Takasaki · Japan	28 °C	-2.4 °C	1,936 mm	78
Kumagaya · Japan	30 °C	-1.3 °C	1,619 mm	98

Planning a trip? See the best time to visit Isesaki.

QuestionsCommon questions about Isesaki’s climate

When is the best time to visit Isesaki?

That depends on what you want, so the honest answer is a comparison rather than a single month. May, June, September sit closest to 20 °C on average, August is the warmest month and December the driest. The month-by-month table above has the full picture.

How hot does Isesaki get?

In August, the warmest month, daily highs average 29 °C. About 22 days a year pass 30 °C. The highest value in the 1991–2020 record is 40 °C.

How cold does it get in winter?

Nights average -1.9 °C in January, the coldest month. A normal year has 70 nights below freezing.

Which month is wettest in Isesaki?

September, averaging 205 mm over 16 days with rain. The driest month is December with 46 mm. The year as a whole averages 1,476 mm.

Are these figures a forecast?

No. They are 1991–2020 climate normals: the average of thirty years, which describes what a month is usually like in Isesaki rather than what any particular week will bring. Individual years can differ substantially from the normal.

Data sources and method

ERA5 / ERA5-Land reanalysis — Copernicus Climate Change Service (C3S), ECMWF. Copernicus Licence
Open-Meteo — Open-Meteo.com. CC BY 4.0
NOAA OISST v2.1 — NOAA Physical Sciences Laboratory. Public domain
GeoNames — GeoNames.org. CC BY 4.0

Normal period: 1991–2020
Data point: 36.317°, 139.200° (the coordinates the reanalysis values are taken for)
Dataset version: era5-1991-2020-scores1.1
Last processed: 1 August 2026

Measured values come from ERA5 reanalysis and are reproduced unchanged. Calculated by us: monthly rankings, daylight hours, beach and comfort scores. Full formulas are on the methodology page.

Contains modified Copernicus Climate Change Service information 2026. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.